Chris keeps crashing into things. Since he was a toddler and began to walk, his mother called him “clumsy”. He grew up leaving a trail of wrecked china and furniture wherever he went and learned an apologetic smile to cover what he just couldn’t seem to help.

Chris is now 48 and a successful businessman. He still crashes into things. When he was in his early 30s he met a neurologist at a party. The neurologist took one look at him and said “You’re dyspraxic. Did you have a difficult birth?” Dyspraxia, an imperfect ability to organise motor skills, may stem from birth injury but is more likely to be genetic. If twinned with agnosia, the inability to perceive space correctly, the result can be painful clumsiness. To some extent, Chris has educated himself through pain: after you’ve walked into doors a few times, you approach them more carefully.

But in unfamiliar situations he is likely to do himself some minor mischief. And he is hopeless at do-it-yourself tasks.

Chris is amazed by his twin daughters. One is a keen ballet dancer, the other a talented gymnast. Where did they get it from? Was it genetic luck? Was it chance? Was it their Caesarian birth which avoided pressure on their brains?

Sylvie and Chantal are so graceful, they mock their poor old dad. It makes him remember his own childhood. If someone passed him the ball in football, he would probably not be able to kick it back. If he played tennis, the ball might go under or over his racket. Above all, there was the nagging from his mother. “Can’t you be more careful!” she would snap. That would make him nervous and he would tend to jerk or twitch, which could easily lead to more accidents.

Chris passes off his daughters’ jibes. They are only teenagers, after all. They would find something else to complain about were it not his lack of deftness with a drill, or his habit of knocking over glasses.

He did get upset once, though, when he heard them talking about a friend in ballet class. Maxine had failed yet again to dance en pointe. A little plump, she kept wobbling off. Finally, she fell with a crash, burst into tears and refused to try again. “She’s such a coward,” said Sylvie. “I don’t know why she bothers,” said Chantal. “She’s a clumsy pig,” said Sylvie.

Chris hit the roof. Suddenly, he was 11 years old again, in the corridor at his new school, with all his books lying around him. Roger from the sixth form was kicking the books, hissing, “That’ll teach you to push into me, you clumsy pig”. Then a small group of boys joined in: “Clumsy pig, clumsy pig!” And Mr Edwards walked by saying, without kindness, “Clumsy again, Smith?” Some people get lessons really knocked into them.